Elastomeric pellets are prone to blocking, unless specific anti-blocking measures are taken to mitigate the massing issue. Blockiness refers to the lumpy appearance of polymeric particles, often observed in the shipment of polymer pellets in bags, boxes or railcars. In some situations, the entire mass of the polymer particles may form a single lump or a block of consolidated pellets. This can be contrasted with polymer particles that remain free-flowing, regardless of stress, temperature and time spent in shipment.
Calcium stearate (CaSt) and other metal stearates have been used as an anti-blocking agents. However, CaSt is combustible when handled in air. This poses significant risks associated with the handling of the CaSt coated particles, and requires expensive engineering controls (e.g. inert blanketing) to mitigate such risks. Additionally, the end user must also use engineering controls to mitigate handling risks. There is a need for coating compositions with reduced ignition threshold sensitivity and with good anti-blocking properties. Coated polymer compositions are described in the following references: U.S. Pat. Nos. 6,852,787; 7,101,926 and 5,366,645. However, there is still a need for new compositions with reduced ignition sensitivity, and which have improved anti-blocking properties. These needs have been met by the following invention.